Astrogator's Logs

Note: I discovered that today is Left Handers’ Day (there is such a thing?!) and so I decided to reprint an essay that first appeared on Science in My Fiction.

“Light is the left hand of darkness…” – Ursula K. Le Guin

Those who are, like me, left-handed and older than fifty probably recall being forced to write with our right hand and the frustration of using many “handed” tools, including scissors, rulers and computer mice. We also remember being told that left-handers are prone to immune deficiencies, shorter lives, depression, dyslexia, schizophrenia and a host of other woes… and no wonder, given the drizzle of harassment! Finally, there is the conflation of left with evil, wrong or inept in practically all religions and languages (sinister, gauche, linkisch…) not to mention most political systems, especially those which place high value on obedience and conformity.

Left-handedness is genetically determined, although controversy swirls around candidate genes that have been tentatively linked to the trait and the complications supposed to accompany it – most prominently a protein with the impressively lengthy name of Leucine-Rich Repeat Transmembrane Neuronal 1. LRRTM1 is involved in regulation of the synapses, the tips of the neuronal processes where exchange of information takes place by molecules bridging the gaps between cells. Other theories propose that left-handedness may arise from exposure to increased testosterone during gestation. Yet others attribute it to the asymmetry of the human brain, brought about by the appearance of language whose centers almost invariably reside in the left hemisphere (which regulates the right side of the body).

In contrast to the even distribution of paw preferences in our ape cousins, the percentage of human left-handers hovers around 10% regardless of race and culture. The most common explanation for the persistence of the trait was that left-handed warriors had the element of surprise in primitive societies. As a result of this sneakiness, they survived long enough to leave a few like-handed descendants. Notice that this explanation is exclusively male-oriented and also implies that the trait is both monogenic and dominant. In fact, LRRTM1 is maternally silent – but at least in my case, I know that I inherited my quasi-ambidexterity (loaded word!) from my mother’s side. On the other hand, nobody who has met me can conclude that I’m low on testosterone.

From my professional knowledge of biology and my own awareness of what strengths and weaknesses I possess, I hit upon a slightly more flattering explanation for the persistence of the trait. Namely, I decided that left-handed people must be less lateralized in their thinking. This can lead (literally) to crossed brain wires – and hence to such outcomes as dyslexia. But it can also lead to less mental compartmentalizing, more efficient multi-tasking, enhanced ability to see the big picture and to think across boundaries.

Recent results from several neurobiological disciplines lend support to these speculations. Apparently, left-handers do cluster at the two ends of the IQ range; the connections between the two sides of their brain are faster than in right-handers; they often use both hemispheres for language; and they excel at complicated tasks. Lists of southpaws in history show that they are disproportionately represented among mathematicians, scientists, artists and, for better or for worse, among charismatic leaders — from Alexander the Great to Jeanne d’Arc. Moreover, a disproportionate ratio of US presidents since WWII have been southpaws, partly because schoolchildren in an increasingly un-corseted culture were no longer forced into right-handedness. So left-handers may not be a relic of barbaric times, after all. Instead, they may be the hops that add zest to humanity’s beer.